MKS 628A11TBE Baratron Capacitance Manometer – 10 Torr, Heated to 100 °C

Description

Application Scenarios:

A semiconductor fab runs a CVD chamber depositing films from precursor gases that, at room temperature, would happily condense on any cool surface inside the vacuum system — including the inside of the pressure gauge. An unheated capacitance manometer mounted on that chamber starts drifting within weeks: condensable byproducts deposit on the diaphragm or the electrode structure, the zero shifts, and the pressure the controller thinks it is holding drifts away from the pressure actually in the chamber. The consequences are not dramatic failures but something worse — wafers that are subtly out of spec, a process recipe that no longer reproduces, and yield loss that nobody can trace because the pressure log looks perfectly stable.The 628A11TBE​ addresses exactly this. Its sensor sits inside a thermostatically controlled enclosure held at 100 °C, well above the condensation point of most process byproducts, so deposition is minimised at source rather than compensated for afterwards. That same thermal enclosure delivers a second benefit that matters on a busy production tool: it attenuates ambient temperature swings by a factor of at least 35, meaning a 35 °C change in the equipment bay produces less than 1 °C of change at the sensor. On a tool that cycles thermally through process steps and through maintenance openings, that is the difference between re-zeroing every shift and re-zeroing every quarter.The second scenario is a mixed-gas industrial vacuum process — vacuum furnaces, freeze drying, vacuum distillation, gas laser manufacturing. Here the pain point is calibration rather than contamination. Thermal-conductivity gauges (Pirani, thermocouple) and ionisation gauges do not measure true pressure; they measure a gas-dependent proxy, so a gauge calibrated on nitrogen reads wrong on argon, hydrogen, or a process gas mixture. The 628A11TBE​ measures force on a diaphragm, so it reads correctly on any gas without recalibration. For a plant running several different processes through the same vessel, or a recipe that blends gases, that removes an entire category of measurement uncertainty and the calibration records that go with it.

Parameter:

Technical Principles and Innovative Values:

Innovation Point 1: Percent-of-Reading accuracy, not percent-of-full-scale. This is the specification that most repays close reading. A gauge spec’d at 0.25% of full scale gives you ±0.025 Torr of uncertainty everywhere on a 10 Torr unit — at 10 Torr and at 0.05 Torr alike. The 628A11TBE​ is spec’d at 0.25% of reading, so at 10 Torr the uncertainty is ±0.025 Torr but at 0.1 Torr it tightens to ±0.00025 Torr. Since vacuum processes almost always operate well below full scale, percent-of-reading puts the accuracy where the process actually lives instead of wasting it at the top of the range nobody uses.Innovation Point 2: The 100 °C oven as a drift-prevention mechanism. The 628A11TBE​ holds its sensor at 100 °C — the highest of the three grades in the family, where the 627 and 629 run at 45 °C. Two separate benefits follow. Condensable process byproducts cannot deposit on a surface that is kept above their condensation point, which is the dominant cause of zero drift in vacuum process gauges. And the thermal enclosure attenuates ambient variation by a factor of at least 35, so a 35 °C swing in the equipment bay produces under 1 °C of change at the sensor. Both effects compound over months: a heated gauge simply stays calibrated longer, and every avoided re-zero is avoided tool downtime.Innovation Point 3: True pressure measurement, independent of gas composition. The 628A11TBE​ deflects a tensioned Inconel diaphragm against a permanently evacuated reference cavity held below 10⁻⁷ Torr by an internal chemical getter. Because it measures force per unit area, the reading does not care whether the chamber holds nitrogen, argon, oxygen, a corrosive halide, or a mixture that changes mid-recipe. Pirani, thermocouple and ionisation gauges measure gas-dependent proxies and must be recalibrated per gas — the 628A11TBE​ does not, which eliminates both the measurement error and the calibration burden.Innovation Point 4: A sensor designed to survive its own mistakes. Applying an overpressure to a capacitance manometer could in principle destroy it. In practice the diaphragm on the 628A11TBE​ bottoms out against the electrode substrate, mechanically limiting travel, and the unit is rated to withstand 45 psia with minimal or no shift in output. Venting a chamber to atmosphere with the gauge still mounted — an everyday operational error — is survivable rather than catastrophic. That is a meaningful cost-of-ownership feature on tools where an accidental vent would otherwise mean a new transducer and a requalification.Innovation Point 5: Signal conditioning hardened for the real electrical environment. The 628A11TBE​ uses a low-impedance, fixed-frequency bridge driven by a precision oscillator, with the electronics mounted adjacent to the sensor rather than at the end of a cable. The metal case, internal design, surge and ESD suppression networks, and RFI filtering on every input and output are there because these gauges live next to RF plasma generators, switching power supplies and contactors. The practical outcome is a 0–10 VDC signal that does not pick up noise in an environment that would corrupt a millivolt-level bridge output.